The correct calculation method and application of the 21 -day pregnancy rate (above)

Ma Zhi anger 1, 2 Dong Fei 2

(1. State Key Laboratory of Grassland Agricultural Ecosystem, School of Grass Agricultural Science and Technology, Lanzhou University, 730020, Lanzhou, Gansu;

2. One Mu Technology (Beijing) Co., Ltd., Yi Muyun Data Analysis Project Team, Beijing 100102)

I. Introduction

In recent years, many articles in domestic media and publications have discussed the use of the "21-day pregnancy rate" (21-DAY Pregnant Risk) to evaluate the reproductive performance of the cow field.It reflects the importance of the 21 -day pregnancy rate indicator in the reproductive assessment, as well as the domestic dairy breeding industry’s recognition of the indicator.We also see that many domestic articles and materials are still talking about the concept of traditional pregnancy rate, but the name of the 21 -day pregnancy rate of "borrowing" is still calculated by the breeding rate (SR) by the fetal rate (CR).In fact, the calculation rate of the 21 -day pregnancy rate in the real sense has nothing to do with the rate of fetal tires, which causes a certain degree of confusion and misleading to many front -line practitioners.Although the Chinese name "21 days of pregnancy" is expressed through "%", it is actually not simply a proportion. It is more based on the rate at a certain probability that it can make the "speed" of dairy cows pregnant.This is why the English name uses RISK instead of Rate.Except for some technical experts, it is still difficult for many front -line practitioners to fully understand their algorithms, significance and application methods.We have been thinking about how to thoroughly understand the algorithm and significance of this indicator in the simplest way to truly help the pasture to improve the breeding level.Organizing this article we found that the significance of the 21 -day pregnancy rate is here. With the simplest indicator to evaluate the breeding management level of the pasture, it helps us to understand the core and key points in the process of production and reproduction through this indicator, and and the key points in the process of breeding management.Continuously improved.

2. Why use the 21 -day pregnancy rate to evaluate the breeding level of the ranch?

As we all know, breeding is the key to driving a ranch to be profitable. Therefore, as a manager, the level of breeding of the ranch must be evaluated in a timely manner in order to be able to improve and prevent problems in time.Such as: breeding rate (SR), fetal fetal rate (CR), pregnancy test pregnancy rate (PPR), estrus revelation rate (HDR), pregnancy rate (PR), average calf intervel, average number of empty days (Average)Days Open), Average Times Bred, etc., when evaluating the reproductive performance, there is always one -sided and lagging.And many pastures have suffered heavy losses.

Therefore, people have been trying to find an indicator, hoping to comprehensively, timely, and accurately evaluate the reproductive performance of the ranch. Dr. Steve EICKER and Dr. Connor Jameson first proposed the concept of the 21-day Pregnant Risk in the 1980s (21-DAY PREGNANT RISK).This is the key indicator of the comprehensive, timely, and accurate evaluation of the breeding performance of the ranch that people can find. Therefore, many people also call it the "golden indicator". Here we will do it to the industryGreat contributions to pay tribute!

Third, point description

Here are one of the questions that frontline staff often ask questions one by one.

1. Why must the interval be 21 days?

Because the typical estrus cycle of cows is 21 days.Therefore, some people say that the 21 -day pregnancy rate can be calculated according to the natural month. Even if it can be calculated, it is just a concept of stealing. As a result, it is completely unreliable.

2. Why do cows and reserve cows must be calculated separately?

Because the cows are actively discontinued during the number of days of birth, and the reserve cattle actively discontinue the dating period under the date of date, and the active discontinuation period is the basis of the 21 -day pregnancy rate.The management method of cows is completely different from the management goals, so it must not be confused.

3. What is a pregnancy cow (key)?

First introduce the active discontinuation period (VWP, Voluntary Waiting Period), or a voluntary waiting period, the dairy needs to restore the uterus and body for the next pregnancy for a period of time.Breeding, (generally 50 days to 60 days after the cows are produced, youth cattle for more than 365 days), so it is called the active discontinuation period.

But the pregnancy cow is an active discontinuation period. Those who have not yet become pregnant and have not yet set up forbidden and eliminated cows.

4. Why is it difficult to calculate manually by the 21 -day pregnancy rate?

Because the 21 -day pregnancy rate in the real sense is not calculated by multiplied by the breeding rate, the difficult point of calculation is to know the number of ginseng love affair between the 21 days of the statistics (explained later).For large -scale pastures, it is almost impossible to pass manual computing. Even if it costs a lot of energy manual derivation, it is out of date, and the start time needs to be re -deduced to calculate, so it is necessary to use the computer dynamic model for statistics.

5. What is the passing period (key)?

In the calculation of the 21 -day pregnancy rate, the statistics of the relationship period can be most important, and the most difficulty. The affection period that meets the following conditions will be counted as the enthusiastic period.Here we need to introduce the concept of "Time Window". We will take 21 days as a time window. The cattle to be counted are only distributed in different positions of the 21 -day window.Automatic statistics, eventually obtained the number of enrollment periods.

At least half of the time windows have been exceeded (youth cows with 50 days after delivery) at least half of the time window

I did not get pregnant at the beginning of this time period

Know the results at the end of the time period (whether to breed)

It can be matched at half of the time window of 21 days

It is not forbidden (DNB) or eliminating cattle at half of the time window for 21 days

At the 21 days of the 21st day window, there is no in Bull House

The matched definition of each cow exists independently in each 21 -day window

At the same time, the model needs to consider the treatment under different "special" situations. For example, the active offsetting period is set for 50 days. If a cow is calculated in estrus 48 days after birth, it is determined that the date of the abortion is before half the time window or after the time windowSet the forbidden and elimination of cows before halfway or after the time window.

Fourth, algorithm description

In order to facilitate everyone’s understanding, we only choose the state of pregnancy in many influencing factors to give you an example, and the default other conditions have been met.

Case number one:

Suppose there is a pasture now: Ranch A, there is a cow in this pasture, the cow is 001. Its breeding trajectory is shown in the table below.In estrus and pregnancy, pregnancy.

21 days of pregnancy rate = 1 (number of pregnancy bulls)/1 (the number of enrollment affairs) = 100%

All the cows that can be pregnant (in this example are this cow 001) and successfully pregnant in the first 21 days window.The pregnancy rate will always be 100%, even if the ranch will not go to pregnancy after 3 months.Because she successfully became pregnant when she had the first chance, she could only participate in the relationship period of only one. The state in the latter two time windows was pregnant and did not meet the conditions for participation. ThereforeEmpathy period.

Case 2:

Suppose there is a pasture now: Ranch A, there is a cow in this pasture, the cow is 001, and its breeding trajectory is shown in the table below:

21 days of pregnancy rate = 1 (number of pregnancy bull heads)/3 (the number of ginseng affair) = 33% (take for integer)

All the cows that can be pregnant (in this example are this cow 001) without monitoring the epidemic in the first 21 days window, and there is no breeding. The estrus is monitored in the second 21 -day window. After the breedingUnhappy, monitored estrus in the third 21 -day window, and pregnancy after breeding.The 21 -day pregnancy rate is 33%, because she did not succeed in pregnancy until the third chance. The number of pregnancy heads was 1 head, and the number of enrollment period was 3.

Case three:

Suppose there is a pasture now: Ranch A. There are two cows in this pasture, and the cow number is 001 and 002. Their breeding trajectory is shown in the table below:

21 days of pregnancy rate = 2 (number of pregnancy bull heads)/4 (the number of ginseng affair) = 50%

Niu only 001 did not monitor estrus in the first 21 days window, and there was no breeding. It was monitored in the second 21 -day window window.To estrus, get pregnant after breeding.

Niu 002 monitors estrus in the first 21 -day window. After the breeding, it is not available in the second 21 -day window. It is not allowed in the third 21 -day window window.The two cows are pregnant and have four periods of enrollment, so the 21 -day pregnancy rate is 50%.

From the calculation of these three cases, it can be seen that the 21 -day pregnancy rate covers all aspects of reproduction through the number of enrollment. The calculation seems to be very simple.Many of the pregnancy status in consideration of considerations can be increased by the number of bull heads and considerations to increase the difficulty. Therefore, manual computing is almost impossible for large -scale pastures. ThereforeStatistical calculations can be calculated.

5. The calculation results of the pregnancy rate in the DWEB system of 21 days are presented

After entering the production management system of Yima Cloud DWEB Ranch, click "Breeding Management". The first item is the analysis of the "21 Day pregnancy rate" analysis. For details, please refer to Figure 1 and Figure 2.

Figure 1, 21 days of pregnancy rate diagram

Figure 2 and 21 days of pregnancy rate report

Due to space limitations, at the same time, it does not cause too much "burden" to readers. The value and significance of the 21 -day pregnancy rate and the application in production management practice will be in the next article "The Correct Calculation Method and Application of 21 Days of pregnancy" (Push in.